Sprinkler precipitation rates the key to controlling irrigation runoff

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1 Sprinkler precipitation rates the key to controlling irrigation runoff Spray nozzles have a high precipitation rate that frequently results in irrigation runoff. The precipitation rate will vary with pressure and spacing. At 30 psi and spaced in a square pattern the precipitation rate is 1.58 per hour. The triangular pattern has slightly higher precipitation rates due to the tighter row spacing of 13 ft. at ft. 15 ft / hr. 15 ft. 15 ft. Verify the working water pressure at the spray nozzle to be a minimum of 30 psi. In the case of the 15 Series nozzle, any pressure less than 30 psi requires a closer spacing than 15 ft. If the sprinklers are operating at psi and spaced at 15 ft there will be serious coverage (uniformity) problems. Measure water pressure as the circuit operates at the first and last sprinkler on the circuit. Verify spacing to be no greater than the radius. Sprinklers should be spaced in a square or triangular pattern with consistent spacing between heads. Test working water pressure at the first and last sprinkler with a pressure tee and gauge. Verify spacing between heads with a tape measure. At 30 psi spray heads should be spaced at no greater than their series, i.e 15 series at 15 ft, 12 series at 12 ft, etc. 1

2 Rotor sprinklers rotate a single or multiple streams to achieve coverage. In general, the end of the stream from one sprinkler should hit right at the base of the adjacent sprinkler. The pressure requirement at the nozzle is dependent on the spacing and the nozzle installed in the sprinkler. Performance charts indicate a radius(spacing interval) that can be achieved with a particular nozzle at varying pressures. Generally, these sprinklers have a higher pressure requirement than spray nozzles. As a consequence low nozzle pressure is a common problem. Pressure, along with spacing must be verified in the field. Precipitation rate data may only be relied upon when pressure, nozzle, and spacing agree with nozzle performance data. These sprinklers have lower precipitation rates than sprays and therefore can be run for longer periods before runoff occurs. These charts represent precipitation rates at half circle or 180 degree setting. For full circle operation divide the chart values by 2! The pitot tube and pressure gauge are used to measure nozzle pressure which is evaluated against nozzle performance charts 2

3 Suggested maximum run times on clay soil before runoff occurs (on flat surfaces) infiltration rate " / hr spray spray spray rotors rotors rotors rotors rotor 1.6" / hr 1.8" / hr 2" / hr 0.25"/hr 0.35" / hr 0.45"/hr 0.55"/hr 0.65"/hr 4 min 4 min 4 min 24 min 17 min 13 min 11 min 9 min Suggested maximum run times on clay loam soil before runoff occurs (on flat surfaces) infiltration rate " / hr spray spray spray rotors rotors rotors rotors rotor 1.6" / hr 1.8" / hr 2" / hr 0.25"/hr 0.35" / hr 0.45"/hr 0.55"/hr 0.65"/hr 6 min 5 min 4 min 38 min 27 min 21 min 17 min 14 min Low head drainage occurs in lateral sprinkler piping after the irrigation valve has shut down. When heavy clay soils are being irrigated, multiple cycles (usually 6-8) must occur every day that irrigation takes place. This necessary cycling process introduces the problem of low head drainage. This problem may be resolved with addition of check valves which may be retrofitted into the base of spray head bodies. 3

4 It is not unusual to find irrigation valves with spray and rotor type sprinklers plumbed together. This is never acceptable and should be corrected because of the different precipitation rates of the two types! While low pressure at spray nozzles is frequently encountered, it is not unusual to find spray systems with excessive pressure. When pressure exceeds 45 psi, the sprinkler body should have a pressure regulating feature. This feature, like the anti-drain check valve, may be retrofitted into an existing spray body without digging up the sprinkler When sprinkler inlet pressures exceed 75 psi a regulator must be installed at the valve or backflow prevention device location. Spray heads operating at 90 psi. This problem was corrected with the addition of a regulator feature on the valve. Internal pressure regulating device is designed for inlet pressures between 45 and 75 psi Same circuit operating at 30 psi! 4

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6 Managing the Irrigation Controller in a Drought The amount of irrigation water applied to the landscape varies with the type of plant material and the precipitation rate of the sprinklers. The environmental factors that drive plant water use are temperature, wind, solar radiation, humidity, and ground temperature and collectively they generate a number known as Evapotranspiration (ET). These factors are nearly impossible for the landscape manager to evaluate in the field. The State of California has a network of computerized weather stations linked to a free website in a program known as CIMIS (California Irrigation Management Information System). There are nearly 200 of these stations throughout the state. They provide the landscape manager with a number that represents the inches of water plants generally need in a month, week or day. The number available from the local weather station is known as ET O or reference ET. There are many regions of the state that lack a local weather station. In these instances tables are available providing monthly averages in the Water Efficient Landscape Ordinance (WELO) which is also available on line. Water Efficient Landscape Ordinance (WELO) 5

7 Every plant has a different water requirement relative to ET O based upon the landscape coefficient or K L. The primary factor that drives that landscape coefficient is the species factor. Our primary concern in the drought is the water requirement for turfgrass as it consumes the bulk of the landscape water. The plant water requirement ET L is obtained for any period by multiplying the ET O x K L. In a traditional year cool season turfgrass such as fescue, Kentucky Bluegrass, or rye have a species factor of 70 percent or In a drought we reduce this species factor and in turn the landscape coefficient (K L ) to 60 percent or This follows guidelines developed by turfgrass experts at the University of California at Davis and Riverside. July ET L in a traditional year ET O (8.67 ) x K L (0.70 for cs turf) = 6.06 / month July ET L in a drought year ET O (8.67 ) x K L (0.60 for cs turf) = 5.20 / month The water savings associated with this recommendation will save 0.86 in the peak month of July which is a 14% reduction in water use! The development of an irrigation schedule is based on the average daily ET L. In the month of July we have a ET L of The objective is to establish an average daily ET L which in this case is 0.17 per day (5.20 / 31 = 0.17 ). The replacement for every other day watering for turf in a typical July is 0.34 inches. If we were watering on a flat clay surface the infiltration rate or maximum intake rate of the soil is 0.08 inches per hour. It would be necessary to have 4 cycles. This could typically be achieved on one program. Daily Sun Mon Tue Wed Thur Fri Sat Sun Mon Tue ET L Water Water Water Water Tues Thurs Sat Mon a.m. a.m. a.m. a.m. 0.34" 0.34" 0.34" 0.34" Many local water agencies will have watering restrictions that will allow watering two days per week in July. This means more water will have to be applied each irrigation day requiring more cycles ET L Daily Tue Wed Thur Fri Sat Sun Mon Water Water Wed Sun a.m. a.m. replace replace 0.51" 0.68" (3 days x 0.17") (4 days x 0.17") 6

8 On Sunday the turf water requirement is Regardless of the type of sprinkler, the soil infiltration or intake rate of 0.08 for clay (in this case) dictates the maximum amount of water applied to be 0.08 before runoff. Some sprinklers such as rotors and drip apply water more slowly and can have longer run times. Spray type sprinklers have a much higher precipitation rate so their run times to reach runoff are shorter. The sprinkler does not dictate the number of repeats rather it is the soil type! So the number of cycles required is 8 (0.68 /0.08 = 8.5) We are using 8 cycles here because of the limitations of start times available on most controllers. The next step in scheduling is to determine the run time in minutes required for Sunday. We use a simple run time formula RT = ET L (turf water requirement) / PR (precipitation rate) x 60 (constant). In this example the sprinkler is a 15 ft spray spaced square at 30 psi with a precipitation rate of 1.58 / hr. Recall the Wednesday ET L so the run time is as follows ET L (0.68) / PR (1.58) x 60 = 26 minutes. The problem is that the number is not divisible by 8, but we can have different run times to make this work. On Program A we ll water 4 minutes per cycle x 4 starts = 16 minutes. If we did this on program B as well we would be watering 32 minutes. On program B we ll water 3 minutes for a total of 12 minutes run time (4 cycles x 3 min = 12 min) 7

9 We ve completed the schedule for station 1 for the spray heads on the turf for Sunday. The irrigation water that we had to apply (0.68 ) requires 8 repeats and utilized the capabilities of both the A and B programs. The water requirement for Wednesday morning replaces 3 days of turf water use or 0.51 inches of water). On the majority of controllers in the field there are only three programs. We ll use the final program, program C, for station 1 on Wednesday. This is the hottest month of the year and the run time is not ideal but the best that we can do with the flexibility of most controllers. If you have a controller with only two programs or less than three starts per program then replace it. The run time for Wednesday is RT = ETL / PR x 60 (0.51 / 1.58 x 60) = 19.4 min. We ll round up the time to twenty minutes which will give us four, five minute cycles (4 starts x 5 min = 20 min). 8

10 One important feature of more modern controller is the percentage adjust key or +/- key. It allows adjustment of an entire program by percentages. Heavy clay soils and spray heads render this a meaningless feature. Imagine that there is a 4 minute run time that needs a 10% reduction. The controllers times in 1 minute increments so the % key only works for 25% changes (4 minutes reduces to 3 minutes is a 25% change). In the example we have provided. If we wanted to reduce the time by 10 % we would eliminate one of the start times on program B. This would reduce the run tine on Sunday from 28 minutes to 25 minutes. Ultimately we need to be very creative in dealing with reduced watering days. There are many limitations to controller programming and they are acutely felt during a drought. Another serious limitation which will be addressed is the limitation of the water meter to apply water in two days that would normally be applied in 3 to 7 days per week! 9

11 Irrigation Schedule Fair Oaks, CA Pop Up Spray Heads / Cool Season Turf Cool Season Turf with a K T species factor (maximum stress) 0.60 DU LQ 0.56 Every 4th day Every 3rd day PR Rate 1.58 inches / hr. watering watering RTM 1.36 Fair Oaks Fair Oaks Fair Oaks Lower Upper Lower Upper ET O ET O CS Turf Bndry. Bndry. Bndry. Bndry. Avg Avg. Req't Run Time Run Time Run Time Run Time Monthly daily daily min. min. min. min. 31 Mar Apr May Jun Jul Aug Sep Oct MP Rotators / Cool Season Turf Cool Season Turf with a K T species factor (maximum stress) 0.60 DU LQ 0.72 Every 4th day Every 3rd day PR Rate 0.43 inches / hr. watering watering RTM 1.2 Fair Oaks Fair Oaks Fair Oaks Lower Upper Lower Upper ET O ET O CS Turf Bndry. Bndry. Bndry. Bndry. Avg Avg. Req't Run Time Run Time Run Time Run Time Monthly daily daily min. min. min. min. 31 Mar Apr May Jun Jul Aug Sep Oct

12 Drip / Line Source GPH - 12" x 12" spacing Ornamental Shrubs with a species factor K P (max stress) 0.40 DU LQ 0.9 Every 4th day Every 3rd day PR Rate 1.42 inches / hr. watering watering RTM 1.06 Fair Oaks Fair Oaks Fair Oaks Lower Upper Lower Upper ET O ET O Orn. Shrub Bndry. Bndry. Bndry. Bndry. Avg Avg. Req't Run Time Run Time Run Time Run Time Monthly daily daily min. min. min. min. 31 Mar Apr May Jun Jul Aug Sep Oct Drip / Point Source - random spacing " / hr. PR Ornamental Shrubs with a species factor K P (max stress) 0.40 DU LQ 0.9 Every 4th day Every 3rd day PR Rate 0.25 inches / hr. watering watering RTM 1.06 Fair Oaks Fair Oaks Fair Oaks Lower Upper Lower Upper ET O ET O Orn. Shrub Bndry. Bndry. Bndry. Bndry. Avg Avg. Req't Run Time Run Time Run Time Run Time Monthly daily daily min. min. min. min. 31 Mar Apr May Jun Jul Aug Sep Oct Sacramento (916) Rancho Cordova (916) Roseville (916) South Sacramento (916) El Dorado Hills (916) * lower boundary represents a water time that assumes a high uniformity of application DU LQ * upper boundary increases run time to account for normal sprinkler uniformity deficiencies

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15 Measuring irregularly shaped areas Calibration is critical to the effective and safe application of pesticides. Equipment calibration is just part of the process. The often overlooked aspect of calibration is the calculation of the area to be treated. In this regard pesticide application is not unlike area estimation for water use or landscape pre construction When the geometry of an area is complex, the area can be measured by treating it as a circle. The formula for the area of a circle is Pi (3.14) x radius (squared) = A. We can determine the average radius of any shape by measuring the distance from near the center to the perimeter 16 times using a 100 foot tape. We then total these measurements and divide by 16 to obtain the average. In the field use a fabricated 2 x 2 plywood sheet with a hole in the center for a screwdriver and place this sheet near the approximate center of the area to be measured. Create 16 permanent radii from the center at 22.5 degree increments on the plywood sheet. Use these as a guide and measure to the perimeter. For simplicity of calculation inches are converted to a decimal equivalent. A conversion chart for inches to decimal equivalent may be found on the right side of the table on the reverse side of this page. This shape has a total of feet. The average radius is therefore (524.5/16). Find the average radius on the reverse table. We have to interpolate to determine that the area is 3,346 sq. ft 14

16 Conversion Chart - Average Radius to Square Feet (16 radii minimum) Avergage Radius (feet) Area (square feet) Avergage Radius (feet) Area (square feet) Avergage Radius (feet) Area (square feet) Avergage Radius (feet) Area (square feet) , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,751 Decimal Equival , , ,936 inches decimal , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,685 c Ewing Irrigation Produ 15

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18 Spray Circuit - Audit Run Time (4 minutes) Driest 6 catches psi gpm cfm Total Avg. psi (total divided by 6) DU LQ dry 6 Total of 24 catch readings avg of 24 avg.(total divided by 24) DU LQ PR = 3.66 x V avg t r x 16.5 PR Rotating Stream Circuit - Audit Run Time (10 minutes) psi Driest 6 catches gpm cfm Total Avg. DU LQ dry 6 psi (total divided by 6) avg of 24 Total of 24 catch readings DU LQ avg.(total divided by 24) PR = 3.66 x V avg t r x 16.5 PR 16

19 Estimating Irregularly shaped Areas Measurement A B C D E F G H I J K L M N O P EMITTER FLOW (TIME TO FILL 2" CAP) TOTAL AVG/16 EMITTER TYPE GPH FILL TIME SQ. FT POINT SOURCE SECONDS METER POINT SOURCE MIN 52 SECONDS FLOW LINE SOURCE MIN 2 SECONDS CFM LINE SOURCE MIN 4 SECONDS POINT SOURCE MIN 45 SECONDS PR Rate LINE SOURCE MIN 26 SECONDS 17

20 The water meter is an important management tool during the drought. As a landscape professional you can provide a very important service for your customers by monitoring their water use. If you are performing landscape maintenance at a site, then you are visiting it on a weekly basis and it will take just a few minutes to provide this service. Your primary objective in this regard is to look for leaks. Open the valve meter box when you arrive for maintenance and watch the meter for a few moments. There is a low flow indicator on the meter. If the meter is not dedicated to the landscape there may be a flow of potable to the residence or building. Try to check for leaks when no one is present in the building. If the irrigation system is off and no one is home the low flow indicator should not be moving. Observe it for a few seconds to see if it is turning. It may not be turning, but there still may be a leak. Note the position of the needle and the reading on the total flow which looks like a car s odometer. Check this before you leave the site to see if there has been any flow during your maintenance period. Calculate the flow of the leak per hour and multiply by 8,760 (hours per year to determine the amount of water loss per year. At each maintenance visit check the low flow indicator and the position of the needle and total flow to determine if there is a slow leak. Take a digital image with your phone camera to document any leaks as well as the meter number. This is a great low cost service that you can provide to your customers during the drought! The water meter is usually located between the curb and the backflow prevention device. Most commercial sites have dedicated landscape meters but this is not always the case. Meters record water volume in gallons or cubic feet, but most water agencies provide meters that record in cubic feet. A cubic foot of water is 7.48 gallons and is a 12 x12 x12 cube. Customers are billed in what is known as ccf s or hundred cubic foot units of 748 gallons. 18

21 Each full revolution of the dial on commercial meters (1 ½ and larger) represents a flow of ten cubic feet or 74.8 gallons Each full revolution of the dial on a residential meter (5/8, 3,4 and 1 ) represents a flow of one cubic foot or 7.48 gallons The water meter limits the amount of water that can be delivered to the site. Most irrigation systems were designed with the expectation that they would apply water anywhere from three to seven days per week. Take the system that in non-drought years was able to water six days per week and nine hours per day in the month of July. This is a total watering time of 3,240 minutes (6 x 9 x 60). Let s assume this is a 2 meter providing 50 gallons per minute. Under these conditions the meter could provide up to 162,000 gallons per week. (This 50 gpm flow is an average as some stations such as drip have far less flow and others such as large turf rotors have more) Now, transition to a drought where watering is allowed two days per week for a maximum of thirty hours per week. The amount of water that could be delivered to the site would be 90,000 gallons (1,800 minutes x 50 = 90,000. Given this shortfall it is likely the site manager will have to set priorities on landscape watering and it is possible that some areas of the landscape may not survive. Invest the landscape water in large trees and shrubs which have the greatest value in the landscape! meter size meter flow Max. deliverable water in 30 hrs. Sq. ft of turf that may be irrigated in 1 week (1.5" application) 5/8" 15 27,000 28,892 3/4" 22 39,600 42,376 1" 37 66,600 71, /2" , ,462 2" , ,140 3" , ,387 19

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26 Sacramento Tree Foundation Building healthy, livable communities in the Sacramento region by growing the best urban forest in the nation. Air Quality Energy conservation Water Quality Climate change Comfort Habitat Public Health Economy $$$

27 Ideal Soil Moisture at Root Uptake Area Up to 5% OM 25% Water Filled Pore Space 25% Air Filled Pore Space Up to 45% Mineral Solids

28 Tree watering systems are temporary structures Young Tree Mature Tree

29 Trees have many benefits Water monitoring is essential Irrigation structure for trees is temporary Thank you! Luanne Leineke Stewardship Coordinator Sacramento Tree Foundation

30 Caring for Trees in a Drought Trees are generally the most valuable asset in the home and business landscape and when their health declines, the most difficult and expensive to replace. Considering their value, and the time needed to grow to maturity, ensuring the survival of shade trees should be a top priority for landscape professionals. According to local certified arborists, a typical large tree in the Sacramento valley has a replacement value ranging from several to tens of thousands of dollars. During times of drought, landscape retention decisions should be made based on value, risk assessments and the cost and ease of replacing assets of equivalent size. A typical large tree in the Sacramento valley has a replacement value ranging from several to tens of thousands of dollars. With Governor Brown s recent declaration This [is an] emergency and I m calling all Californians to conserve water in every way possible. It is imperative that professionals are able to both meet his call to action as well as preserve the irreplaceable mature tree canopy. Steps for Conserving Water and Growing Healthy Trees Whether trees are planted in turf, mixed beds, or alone, the following steps will help to conserve water while also improving the tree s ability to utilize the water it is offered. Choose Species Wisely Whenever possible, select species that are well adapted to arid climates. Native plants are not always drought resistant, so base decisions on water needs, and not necessarily on origin of the species. Improve Soil Structure Properly aerated soil is an essential factor for the functioning of a tree s root system and water permeability. n Remove excess soils burying the flare of the tree trunk in a careful manner to minimize damage to the root system. n Remove rocks and other impervious materials from beneath the tree canopy. n Aerate the lawn so that roots of mature trees are better able to access water and oxygen. Reduce Competition n Remove all weeds and grass within three feet of the base of young trees. For trees planted alone or in mixed beds, this is also recommended. Mulch Leaves and ground wood are ideal mulch materials. Organic mulch will break down and create nutrient-rich compost that will keep soil evenly moist, conserve water, and insulate roots while providing essential nutrients for the tree. n Place mulch 4 to 6" deep, keeping it 4" away from the trunk, around all trees where the landscape allows. Monitor Soil Moisture Place a shovel, small spade or a screw driver into the soil to a depth of 6 8" (near the trunk for a young tree and under the drip line for a mature tree). Squeeze a handful of soil, if it feels dry and crumbly add water.

31 Recently Governor Brown proclaimed, This year, we celebrate Arbor Day as the state confronts one of the most severe droughts on record. In the spirit of preserving trees for future generations, Californians are advised to honor this occasion by planting drought-tolerant trees and learning best practices in caring for trees during a water shortage. All trees need regular, deep watering when soil moisture is low. The best watering solution is a dual system of drip emitters and sprinklers which maximizes irrigation efficiency for young and maturing trees. However, as water restrictions increase we must utilize other watering techniques to ensure trees, whether newly planted or mature, receive the water they require to survive. As water restrictions increase we must utilize watering techniques to ensure trees, whether newly planted or mature, receive the water they require to survive. Young Saplings (between one and three years of age) and Maturing Trees (ages 4 to 15) Mature Trees (A mature tree is defined as fifteen years or older.) It is imperative that young trees receive water regularly to their root ball throughout their first three years in the ground. Mature trees vary widely in their need for water, depending on size, age, species, soil types and slope. The water needs of most tree species planted in turf are generally met by the relative high water needs of turf. With restricted water use, it is likely turf will no longer be irrigated. This could have drastic effects on mature trees that are used to regular lawn watering. During this time, it is very important to deeply water the tree. n Apply five to ten gallons of water per week during mild weather. During the hot summer months, young trees may require up to 15 gallons of water per week. Lawn watering does not provide sufficient water for a young tree as the root area is not extensive enough to absorb water irrigated over a large area. n The best way to focus water on the tree s rootball is to form a small temporary earthen berm/watering well around the tree, about 2 3 feet in diameter and about 4 6 inches high. Fill it slowly by placing a garden hose near the base of the trunk and set it at a slow flow. n As trees grow, expand the temporary earthen berm to cover the enlarged root system or apply water to the soil outside the edge of the root ball to one foot beyond the drip line (the soil beneath the edge of the leaf canopy). Increase the amount of water to soak the expanding root area to a depth of at least 8 inches. n Trees do not grow or fair well in soil that is constantly wet it is best to let the ground dry out between waterings. As the daytime temperatures increase water more frequently. Check the moisture of the soil before watering. n The best way to water a mature tree is to apply the water slowly and uniformly using lowvolume application equipment. One option is to use Drip Line a soaker hose spreading it around the tree to at least one Soaker Hose foot beyond the drip 1ft Beyond Drip Line line (the soil beneath the edge of the leaf canopy) and allowing the water to penetrate so that the soil under the tree becomes saturated to a depth of about 8 12". n The general rule for mature trees is deep, infrequent irrigation. Frequency of watering depends on temperature, shade cover and presence of mulch. Trees need oxygen as much as water. Allow the soil to dry between waterings for most mature trees one deep watering per month is adequate. If you are concerned about the health of a mature tree, your best choice is to hire a Certified Arborist. A list of Certified Arborists by zip code can be found listed at Sacramento Tree Foundation 191 Lathrop Way, Suite D Sacramento CA, (916) 924-TREE sactree.com